As Kory mentioned, you can't assume that something is balanced or not balanced based on a singular experience. Imbalance can only become a conclusion over a longer period of testing, and the effects of layered armor on DPS balance are well-documented and tested. It's not good.

In Atonement's ALPHA, I countered armor layering by GREATLY increasing the population and power-level of dangerous NPCs. The only time in SOI3's history where the NPC population came close to resembling Atonement ALPHA's was during Alcarin and Fulgrim's spider invasion of the woods north of Utterby. For those that remember the two day RPT to rid the forest of those spiders nests, keep in mind that ARPI ALPHA constantly loaded numbers similar to - and greater than - those numbers.

It's the population of dangerous mobs that allowed for speedy skillgains, as the skillgain system begins to take into account how many mobs you are being targeted by as a pre-requisite for skillgain at certain levels.

That said, keeping armor layering in the game would demand the release of Good Quality weapons and MUCH more deadly mobs + population. The armor in SOI3 is already stronger than the armor PCs had in Atonement, and allowing that armor to be layered only compounds the issue of weapons and mobs not being as strong, comparatively.

SOI3's training wheels in terms of danger and resource scarcity/economy is one of it's most significant issues. Armor Layering (and dual-wielding medium-sized weapons) are the greatest damnable offenses to that issue on the combat side of things, currently.

I don't have a conceptual issue with armor layering. I just have an effective issue with the code, itself, based on experience.

Icarus has said that he's now gone in and fixed the code to ignore the issues we had with it in Atonement, so that layering armor only gives a standard +1AC bonus (effectively), and compares the damage-type against the armor-type of the top layer of armor.

If this is true, then I don't have any complaints with the fix. It seems fair and balanced to me, and I'm grateful for the prompt researching and fix.

What I am saying is that two primary armors layered like what you posted didn't actually have any combat-related coded effect besides encumberance. There was a rather amusing side effect that only happened with certain very specific armor_types and AC combined when on primary over secondary armor. It was actually not achievable in game on body armor at all, for example.

all this debate is confusing me. What coded advantages does wearing a gambeson underneath chainmail give, exactly?

A really bad sword with a short blade lies here. look sword This sword hardly even a sword. It's kind of really just a piece of metal bent like a sword. Its blade is rather short. Kind of pathetic, really.